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Thread: 3.0L Megasquirt w/ EDIS: Headers running at different temps?

  1. #11
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

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    My VIN:    767 (3.0L EFI/EDIS)

    Dave: I'll have to look for a curb idle screw. I didn't notice one, but that doesn't mean that there isn't one there.

    FABomjoy: I'll try adding fuel (which I assume I do with the VE; I'm still figuring this out) and flattening the idle area next weekend, and post the resulting MSQ then. The one I'm using now is basically at defaults, but Josh's MSQ had pretty much identical results. The fact that the driver's side exhaust is 3x hotter than the passenger side is still perplexing, though, and it seems like adjusting the VE table isn't going to do much for that, will it?

    Thanks!

    -- Joe

  2. #12
    '82 T3 FABombjoy's Avatar
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    There are several reasons half the engine is running differently and we could at least rule out the tune with the msq file.

    Off the top of my head a few reasons could be:
    -wiring differences between injector bank A and B (flipped polarity on half?)
    -different injector characterization for A/B
    -incorrect cam timing (which you alluded to)
    -intake gasket - not familiar enough with the 3.0 intake to know if this is a thing like the fairly split manifold on the 2.8
    -plugged/imbalanced exhaust
    Probably more than this.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

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  3. #13
    Not a DeLorean Guru
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    Have you hugged the car?
    -Mike

    My engine twists my frame.

    1981 DeLorean, Carb LS4 swap completed
    1999 Corvette, cam/headers/intake manifold, 400 rwhp
    2005 Elise, stock
    2016 Chevy Cruze

  4. #14
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

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    My VIN:    767 (3.0L EFI/EDIS)

    Quote Originally Posted by FABombjoy View Post
    There are several reasons half the engine is running differently and we could at least rule out the tune with the msq file.

    Off the top of my head a few reasons could be:
    -wiring differences between injector bank A and B (flipped polarity on half?)
    -different injector characterization for A/B
    -incorrect cam timing (which you alluded to)
    -intake gasket - not familiar enough with the 3.0 intake to know if this is a thing like the fairly split manifold on the 2.8
    -plugged/imbalanced exhaust
    Probably more than this.
    Thanks!

    The injector A/B bank wiring occurred to me last night -- I'll definitely check that this weekend. Ironically, with the throttle open slightly (I mean, before I fixed it so the cable closes it all the way this weekend), the passenger side was double the temperature of the driver's side -- so, the opposite of what I'm seeing now.

    I'm not sure what you mean by different injector characterization.

    Still trying to avoid having to check the cam timing, so I'll do everything else first.

    The 3.0L intake manifold is a of a single main body with arched pipes that go to each cylinder. I'd probably have had to screw up the gasket on all three pipes on that side to have such a constant temperature there. That's not to say I didn't do that, but it does seem less likely.

    The exhaust is pretty balanced -- short pipes from the headers to the cats, then slightly longer pipes to a dual in/dual out muffler. Admittedly, I'm using the muffler in a non-conventional manner (they intended both inlets to be on the same side; I have half of the engine using the "top" of the muffler while the other uses the "bottom"). Pipes are all about the same length. It's definitely not plugged on either side.

    I'll check on the wiring, and if all else fails, the cam timing, this weekend.

    Thanks again

    -- Joe

  5. #15
    EFI'd dn010's Avatar
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    I know you're trying to avoid it, but I'd start by pulling your valve covers and seeing if the valve timing is in order. I'd imagine the 3.0 book should have valve timing specs as far as when the intake / exhaust valves should open and close per side. That should save you from removing the timing cover if you don't need to and will also rule out mechanical error instead of software.
    Last edited by dn010; 07-16-2018 at 12:15 PM.
    -----Dan B.

  6. #16
    Senior Member
    Join Date:  May 2011

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    Quote Originally Posted by dn010 View Post
    I know you're trying to avoid it, but I'd start by pulling your valve covers and seeing if the valve timing is in order. I'd imagine the 3.0 book should have valve timing specs as far as when the intake / exhaust valves should open and close per side. That should save you from removing the timing cover if you don't need to and will also rule out mechanical error instead of software.
    Yup, the manual says this:

    Intake Valve Open: 14 degrees BTDC (before top dead center)
    Intake Valve Closes: 48 degrees ABDC (after bottom dead center)
    Exhaust Valve Opens: 56 degrees BBDC (before bottom dead center)
    Exhaust Valve Closes: 12 degrees ATDC (after top dead center)
    Valve Overlap: 26 degrees
    Intake Duration: 252 degrees
    Exhaust Duration: 248 degrees

    I'm guessing I can test cylinder 1 by rotating the engine to 14 degrees (based on the gauge on the timing cover) and seeing if the intake valve has just closed, right? And I could estimate the position of the other cylinders by counting teeth on the crank pulley gear, I imagine.

    Thanks!

    -- Joe

  7. #17
    LS Swapper Josh's Avatar
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    ^ you are on the right track here checking the timing.
    This very much seems like a mechanical problem, not a tune problem.

    Please eliminate all mechanical issues before you start modifing the tune, or you may just make the situation worse.
    But like Luke said trust the wideband.

    5.3L LS4 + Subaru 6spd 314whp/348ft-lbs
    Getting it back on the road!
    LS Swap

  8. #18
    '82 T3 FABombjoy's Avatar
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    Quote Originally Posted by jangell View Post
    I'm not sure what you mean by different injector characterization.
    Injector deadtime curves. It's possible to have accidentally set a different curve for bank A and B.

    Quote Originally Posted by Josh View Post
    This very much seems like a mechanical problem, not a tune problem.
    It does, especially since the 3.0 is even fire (megasquirt does not warn you if setting up oddfire ignition without cam input). Was just hoping to find some magic in the msq first!
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

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  9. #19
    LS Swapper Josh's Avatar
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    Im pretty confident that the tune is not causing this issue. I have about 30,000 kms on it after all. Not to say it wont need some tweaking, but nothing this major.

    5.3L LS4 + Subaru 6spd 314whp/348ft-lbs
    Getting it back on the road!
    LS Swap

  10. #20
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    864

    My VIN:    767 (3.0L EFI/EDIS)

    Here's my MSQ and the last log I made on Sunday. The MSQ is one I built myself before I got Josh's (I've attached it as well). I did a side-by-side comparison of his and mine a while back and there are some minor differences, but they're overall pretty close. I decided to go with my tune for now, although when I did run Josh's it ran smoother. It's entirely possible I screwed up something. At one point I had the displacement wrong (I think I typed 2795 instead of 2975 or something like that), for example.

    My Tune: Joe-CurrentTune.msq
    Latest Log: 2018-07-15_10.54.16.msl

    Josh's Tune: Josh-KnownGoodTune.msq

    -- Joe

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